Dateadd Confusion

I am trying to find a group of clients that were entered last week. I am getting all the dates to go with the Monday of the week they were entered. i.e. If they were entered on 8-2 or 8-3, they go with 8-1. If they were entered, 8-9, they will be under the 8-8 Monday.

No problem with finding the Mondays using either the nice 'weekcommence' function I found here or using numerous t-sql examples.

One thing I don't understand is- how come I can't use an equal sign in my syntax?

For instance,

SELECT dbo.weekcommence(date_added)
FROM clients
where dbo.weekcommence(date_added) = dateadd(wk, -2, GETDATE() )

won't return any results. If I use a greater than sign, I get this week, 8-8 and last week 8-1. I only want to see the week of 8-1.

Now- look at what I have below: Shouldn't I really be able to see ONLY last week's Mondays with this?

select dateadd(wk, -2, dbo.weekcommence(date_added))from clients

To me- the way this reads is: show me 2 weeks ago, from these dates (first Mondays function).
The results are the last two MONTHS, not weeks. What am I misinterpreting?

I can also use this:

SELECT dbo.weekcommence(date_added) FROM clients
WHERE (dbo.weekcommence(date_added) >= dateadd("d",-7,DATEADD(wk, DATEDIFF(wk,1,getdate()), 0)))

and get the week's of 8-1 and 8-8. But I can't get JUST 8-1 if I take out the greater than sign.

To me- this one reads: Select all my Mondays from the function. Show me Mondays from my function that are = 7 days from this Monday's date.

It seems like it should be straightforward, but I'm obviously missing something big. Any help?